mark all dtors which are virtual because base class dtor is virtual explicitly virtual themselves

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41020 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/cocoa/glcanvas.h

@@ -32,7 +32,7 @@ public:
         const wxPalette& WXUNUSED(palette),
         const wxGLContext *other /* for sharing display lists */ );
 
-    ~wxGLContext();
+    virtual ~wxGLContext();
 
 
     void SetCurrent();